In a metallic-roughness PBR material, base color provides diffuse reflectance for non-metals and reflectance color for metals.

Typical color space
sRGB
Avoid
Baked directional lighting
Related channels
Roughness + metallic
glTF term
baseColor

One map, two material roles

For dielectric surfaces it mainly represents diffuse color. For metallic surfaces it colors the reflected light, while the diffuse contribution is suppressed by the shader.

Check it without environment lighting

Use a channel-isolation view to spot unwanted highlights, cast shadows, seams, or inconsistent exposure in generated texture data.